To each \(x\in N \rtimes _{\alpha } \Gamma \)  one can associate a function \(x: \Gamma \rightarrow N\)  with the idea that \(x\)  is represented by \(\sum \pi _{\alpha }(x(g))\lambda (g)\) . It is well known that this function uniquely determines \(x\)  ([1]}, p.366, [2]}, p.284). However the convergence of the series does not take place in any of the usual topologies on \(N\rtimes _{\alpha } \Gamma \)  ([3]}).
